1. Field of the Invention
The present invention relates to well completion equipment, and more specifically to a mechanism for remotely actuating a downhole well tool that requires pressurized hydraulic fluid to operate.
2. Description of Related Art
Well completion equipment is used in a variety of well related applications involving, for example, the production of fluids. The completion equipment is deployed in a wellbore and requires power to operate, or shift from position to position in accordance with each device's intended purpose. The actuation of these downhole devices is typically accomplished by running a hydraulic control line or lines from the well surface, through the well to the device and then, by applying pressure through the line, the device can be made to operate.
There are a number of disadvantages with such an arrangement. The most obvious is the difficulty in installing a control line through a deep or extended well. As the control line may be required to pass through different zones in the well, it must be adapted to pass through or around all the devices which are present in the well bore. As some of these devices may be packers used to seal sections of the well tubing, it is difficult to make a connection through a packer and maintain the sealing integrity required of the packer. Additionally, as these lines are kept as small as possible so as to be unobtrusive, they have narrow diameters, which results in slow response times if the device is located deep in the well. Yet further there are typically a number of devices located in the completion tubing. As a result multiple hydraulic control lines must be run from the surface through the well. This adds to the complexity of running a completion string.
In an attempt to over come some of these difficulties, hydraulic actuators have been developed which enable multiple devices to be operated from a single hydraulic control line. A single hydraulic power source is located at surface and a main control line is run into the wellbore to the actuator. As the hydraulic power source is still located at the surface, the response times can be slow. Additionally, in order to use a single control line, the devices typically operate in a defined sequence, the order being determined from the actuator arrangement. This limits the speed of response further as each device in the sequence must be operated before the desired device can be made to operate. Additionally as all the devices are working from a single control line, any failure of the control line and/or the actuator can render all the devices inoperable. The speed of response can be increased by using multiplexers and enhancers. These unfortunately add to the space required for the actuator in the well bore and increase the complexity of the arrangement making it difficult to install and prone to failure.